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* [PATCH] x86: signal: check signal stack overflow properly
@ 2009-03-19 17:56 Hiroshi Shimamoto
  2009-03-20 18:03 ` [tip:x86/signal] " Hiroshi Shimamoto
  0 siblings, 1 reply; 6+ messages in thread
From: Hiroshi Shimamoto @ 2009-03-19 17:56 UTC (permalink / raw)
  To: Ingo Molnar, Thomas Gleixner, H. Peter Anvin; +Cc: linux-kernel

From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>

Impact: cleanup

Check alternate signal stack overflow with proper stack pointer. The stack
pointer of the next signal frame is different if that task has i387 state.

On x86_64, redzone would be included.

No need to check SA_ONSTACK if we're already using alternate signal stack.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
---
 arch/x86/kernel/signal.c |   48 +++++++++++++++++++++++++--------------------
 1 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 4da412a..62f2164 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -211,31 +211,27 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 {
 	/* Default to using normal stack */
 	unsigned long sp = regs->sp;
+	int onsigstack = on_sig_stack(sp);
 
 #ifdef CONFIG_X86_64
 	/* redzone */
 	sp -= 128;
 #endif /* CONFIG_X86_64 */
 
-	/*
-	 * If we are on the alternate signal stack and would overflow it, don't.
-	 * Return an always-bogus address instead so we will die with SIGSEGV.
-	 */
-	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - frame_size)))
-		return (void __user *) -1L;
-
-	/* This is the X/Open sanctioned signal stack switching.  */
-	if (ka->sa.sa_flags & SA_ONSTACK) {
-		if (sas_ss_flags(sp) == 0)
-			sp = current->sas_ss_sp + current->sas_ss_size;
-	} else {
+	if (!onsigstack) {
+		/* This is the X/Open sanctioned signal stack switching.  */
+		if (ka->sa.sa_flags & SA_ONSTACK) {
+			if (sas_ss_flags(sp) == 0)
+				sp = current->sas_ss_sp + current->sas_ss_size;
+		} else {
 #ifdef CONFIG_X86_32
-		/* This is the legacy signal stack switching. */
-		if ((regs->ss & 0xffff) != __USER_DS &&
-			!(ka->sa.sa_flags & SA_RESTORER) &&
-				ka->sa.sa_restorer)
-			sp = (unsigned long) ka->sa.sa_restorer;
+			/* This is the legacy signal stack switching. */
+			if ((regs->ss & 0xffff) != __USER_DS &&
+				!(ka->sa.sa_flags & SA_RESTORER) &&
+					ka->sa.sa_restorer)
+				sp = (unsigned long) ka->sa.sa_restorer;
 #endif /* CONFIG_X86_32 */
+		}
 	}
 
 	if (used_math()) {
@@ -244,12 +240,22 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 		sp = round_down(sp, 64);
 #endif /* CONFIG_X86_64 */
 		*fpstate = (void __user *)sp;
-
-		if (save_i387_xstate(*fpstate) < 0)
-			return (void __user *)-1L;
 	}
 
-	return (void __user *)align_sigframe(sp - frame_size);
+	sp = align_sigframe(sp - frame_size);
+
+	/*
+	 * If we are on the alternate signal stack and would overflow it, don't.
+	 * Return an always-bogus address instead so we will die with SIGSEGV.
+	 */
+	if (onsigstack && !likely(on_sig_stack(sp)))
+		return (void __user *)-1L;
+
+	/* save i387 state */
+	if (used_math() && save_i387_xstate(*fpstate) < 0)
+		return (void __user *)-1L;
+
+	return (void __user *)sp;
 }
 
 #ifdef CONFIG_X86_32
-- 
1.6.1.2


^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2009-04-09 12:22 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-03-19 17:56 [PATCH] x86: signal: check signal stack overflow properly Hiroshi Shimamoto
2009-03-20 18:03 ` [tip:x86/signal] " Hiroshi Shimamoto
2009-03-24 22:00   ` Oleg Nesterov
2009-03-26 17:03     ` Hiroshi Shimamoto
2009-04-01 15:16       ` [tip:x86/urgent] x86: signal: check sas_ss_size instead of sas_ss_flags() Hiroshi Shimamoto
2009-04-09 12:22   ` [tip:x86/signal] x86: signal: check signal stack overflow properly Jaswinder Singh Rajput

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